Pressure Routing for Underwater Sensor Networks

Pressure Routing forUnderwater Sensor Networks

Uichin Lee (Bell Labs, Alcatel-Lucent)Paul Wang, Youngtae Noh, Mario Gerla (UCLA)Luiz F.M Vieira (UFMG)Jun-Hong Cui (University of Connecticut)

SEA-Swarm

2 | Pressure Routing for Underwater Sensor Networks | March 17, 2010 Copyright © 2010 Alcatel-Lucent. All rights reserved.

SEA-Swarm (Sensor Equipped Aquatic Swarm) Monitoring center deploys a large # of mobile u/w sensors (and

sonobuoys) Mobile sensors collect/report sensor data to a monitoring center Monitoring center performs data analysis including off-line localization Short-term “ad hoc” real-time aquatic exploration: oil/chemical spill

monitoring, anti-submarine missions, surveillance etc. Radio

signal (WiFi)GPS

Sonobuoy

Monitoring center

Data analysis

Pictures from: http://jaffeweb.ucsd.edu/node/81

Example: UCSD DroguesAcoustic modemPressure (depth) sensorDepth control device+ Other sensorsAcoustic

Communications


Problem Definition SEA-Swarm challenges:

Acoustic comms: energy hungry (~W), low bandwidth (<100kbps), long propagation delay (3x10^3 m/s)

Node mobility due to water current (<1m/s) Ground sensor routing protocols do not work well in underwater

High protocol overheads, e.g., route discovery (flooding) and/or maintenance Not suitable for bandwidth constrained underwater mobile sensor networks

(collision + energy consumption) 3D geographical routing (stateless, local) has the following limitations:

Requires distributed underwater localization (+location service) Efficient recovery from a local maximum (like face routing) is not feasible

(Durocher et al., ICDCN’08)


HydroCast: Underwater Pressure Routing HydroCast: 1D geographic anycast routing (to any one of the sonobuoys)

Using measured pressure level (or depth) from on-board pressure sensor A packet is forwarded to a node that is closest to the water surface (or the lowest

depth node in one’s neighbors)

2

SAdvance Zone

distance

erro

r

error

Local max?

Packet drops due to channel errors:requires a robust forwarding

mechanismStuck at local maximum:

requires a recovery mechanism


Opportunistic Routing Handle channel errors by opportunistic routing:

Opportunistic packet receptions thanks to broadcast nature of wireless medium

Any node that has received the packet correctly (called forwarding set) can forward the packet to next hop

Existing opportunistic routing protocols: Anypath Routing based on extended link-state algorithms

ExOR, Least Cost Opportunistic Routing (LCOR) Not suitable for SEA-Swarm due to overhead (network-wide link state flooding)

Geo-Opportunistic Routing (GOR) based on stateless position-based algorithms Geographic Random Forwarding (GeRaF), Contention Based Forwarding (CBF),

Focused Beam Routing (FBR)


Geo-Opportunistic Routing (GOR) GOR: (1) A packet is broadcast; (2) each node determines its own

priority based on its distance to the surface (priority is scheduled using distance based timer); (3) high priority node’s transmission suppresses low priority nodes’ transmissions

Hidden terminal problem: redundant transmissions + collisionsSurface

S

1

Advance Zone2

3

Node 3 fails to suppress its transmission: Need to carefully select a forwarding set that is hidden-

terminal free


Geo-Opportunistic Routing (GOR) Finding hidden terminal free forwarding set is the max clique problem

(hard!) Forwarding set selection heuristic: geometric shape facing toward the

destination Example: fan shape (FBR) or Reuleaux triangle (CBF) Surface

S

1

Advance Zone

Problem: this selection heuristic often fails to maximize progress

Expected progress:

Original: d(1)*p(1)New: d(1)*p(1) + d(2)*(1-p(1))*p(2)d(i): node i’s progress (meter)p(i): prob. node i successfully receives a packetd(i)*p(i) = normalized progress

2d(2)

d(1)


HydroCast: Forwarding Set Selection (Clustering) 1. find node i that has the greatest normalized progress: d(i)*p(i)

2. include all nodes whose distance from node i is in βR (R tx range, β=0.5) 3. if other neighbors are left, clustering proceeds starting from the remaining

node with the highest normalized progress (i.e., repeat step 1 and 2). 4. each cluster is then expanded by including nodes whose distance to any

node in the cluster is smaller than R (node can hear one another) 5. select the cluster with the greatest expected progress as a forwarding set

Surface

1

Advance Zone

23

4

Cluster A:

ExpectedProgress

Expected Progress:Cluster A: d(1)*p(1) + d(2)*(1-p(1))*p(2) + d(3)*(1-p(1))(1-p(2))*p(3)Cluster B: d(3)*p(3) + d(4)*(1-p(3))*p(4)

d(i): node i’s progress (meter)p(i): prob. node i successfully receives a packetd(i)*p(i) = normalized progress

Cluster B:


HydroCast: Recovery Mode No efficient recovery method in 3D geographic routing (Durocher et al.,

ICDCN’08) State-of-the-art “stateless” recovery method: random walk (Flury et al., INFOCOM’08)

Limitation of random walks in SEA-Swarm Due to vertical routing, any nodes below the local max need to repeatedly perform

random walks HydroCast: local lower-depth-first recovery (stateful approach)

Each local max builds an escape path to a node whose depth is lower; after one or several path segments that go through local maxima, we can switch back to greedy mode

Recovery path

Recovery path

A node knows whether it is in

local max or not

Path discovery is still expensive: hop-limited 3D flooding


HydroCast: Recovery Mode

X

C

B

A

Vector D1

2D floor surface flooding for recovery path discovery Only nodes on the envelope (surface) participate in path discovery

Surface node detection Non-surface node: if a node is completely surrounded by its

neighboring nodes Every direction has a dominating triangle

Detection: tetrahedralization with length constraint (tx range) intractable

Detection heuristic: pick k random directions; for each direction, check if there’s a dominating triangle; otherwise, a node is a surface node

SEA-swarm’s floor surface X’s dominating triangle in direction D1

X

C

B

A

D

X: Non-surface node


Simulation Setup QualNet 3.9.5 enhanced with an acoustic channel model

Urick’s u/w path loss model: A(d, f) = dka(f)d where distance d, freq f, absorption a(f)

Rayleigh fading to model small scale fading Acoustic modem:

Modulation method: BPSK (Binary Phase Shift Keying) Tx power: 105 dB u Pa, data rate: 50Kbps, tx range: ~250m

Nodes are randomly deployed in an area of “1000m*1000m*1000m” Mobility model: 3D version of Meandering Current Mobility (MCM) [INFOCOM’08]

2D area: 8km*80km

Example trajectories of three nodes: s1, s2, s3

Plot of streamfunction

2D area at a certain depth


Results: Forwarding Set Selection HydroCast’s clustering is very close to the optimal solution Vertical cone based approach (CBR, FBR) performs poorly

When density is low, its performance is even lower than NADV

Expe

cted

Pro

gres

s (m

)

Number of nodes in the advance zone

12

34Clustering

Cone-Vert

Advance zone

NADV: max d(i)*p(i)max normalized progress

OptimalClustering

ConeCone-Vert

NADV

Con-Vert

NADV


Results: HydroCast Performance HydroCast w/ SD-R performs the best

SD (surface detection): SD-R (our heuristic), SD-A (angle-based, 60˚) DBR performs better than HydroCast w/o recovery (due to multi-path

delivery)

Pack

et d

eliv

ery

rati

o

Number of nodes

HydroCast w/ Recovery (SD-R)

HydroCast w/ Recovery (SD-A)

Depth Based Routing (DBR)HydroCast w/o Recovery

DBR HydroCast w/o recovery

60˚

SD-A

12

4

3

Advance zone

DBR: depth-based threshold5

Forwarding set

Depth Based Routing: DBR


Conclusion Hydraulic pressure-based anycast routing allows report time-critical sensor

data to the sonobuoys on the sea level using acoustic multi-hopping HydroCast:

Novel opportunistic routing mechanism to select the subset of forwarders that maximizes greedy progress yet limits co-channel interference

Efficient dead-end recovery mechanism that outperforms recently proposed approaches (e.g., random walk, 3D flooding)

Research directions: Mobility prediction (using low power sensors) Dynamic topology control/maintenance

Mechanical (depth control/replenishing) + electronic (transmission power)

Pressure Routing for Underwater Sensor Networks

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